code: def backend_cls(self):
      return TestBackend
  
file_path: ray/python/ray/train/tests/test_minimal.py
imports: import pytest
  import ray
  from ray import train
  from ray.train import ScalingConfig
  from ray.train._internal.worker_group import WorkerGroup
  from ray.train.backend import Backend, BackendConfig
  from ray.train.data_parallel_trainer import DataParallelTrainer
  from ray.train.tests.util import create_dict_checkpoint, load_dict_checkpoint
label_desc: Use image node_id 1 for calling the TestConfig obj's underlying member method code with example usage: obj.backend_cls() and returns: TestBackend